Freezing rain causes power outages throughout N.S.

Tens of thousands of Nova Scotia Power customers across the province lost power early Monday morning after freezing rain caused transmission issues.

About 56,000 customers in Halifax, Dartmouth, Antigonish County, Port Hawkesbury and Cape Breton Regional Municipality lost power around 5:30 a.m.

Matt Drover, a senior manager with the utility, said there was a significant amount of ice buildup on the high-voltage transmission line that connects Nova Scotia and New Brunswick. Freezing rain fell on the region throughout the weekend.

Drover said the ice buildup led to an outage on that line, which was causing the system to become unstable, with fluctuations in the grid. 

Listen to Matt Drover's interview with Information Morning Nova Scotia:

Power cut to stabilize system

In order to stabilize the system, Drover said Nova Scotia Power needed to reduce overall electricity demand, so the utility shut off power to several areas, including parts of Halifax, Dartmouth, Truro, New Glasgow and Sydney.

He said it was a safety precaution to make sure the electrical equipment wasn't damaged. 

"If the electrical equipment is damaged, it can take a pretty significant period of time to repair it," Drover told CBC Radio's Information Morning Nova Scotia on Tuesday. "We have lots of backup equipment to use, but just to be on the safe side the best thing to do to avoid damaging that equipment is to interrupt power."

Drover said when the utility needs to reduce customer load, it makes the decision on where to cut power based on the size of the circuit running from the substation to customers, targeting areas with lots of customers.

"So the bigger ones are the ones that we target and we do it in a geographical distribution as well. So not just in one pocket, we try to distribute it amongst the province.… The most customers makes it the easiest to do quickly."

Once the transmission line was reconnected, customers began to have their power restored, and all affected customers had their power restored by 8 a.m.

Other scattered outages lasted longer on Monday, mostly in Cumberland and Colchester counties as well as Cape Breton. Most of those outages were caused by freezing rain, Drover said.

While Drover said it's uncommon for ice buildup to lead to this kind of outage, he expects it could happen more often with climate change.

"Our engineers are constantly looking at ways to storm-harden our system, if you will, to install higher class poles, more resilient equipment and we continue to really focus on vegetation management as well," he said.